"“It is a grotesque concept but they are using people who are clearly mentally subnormal,” the official said. “We know they have clever radicalisers who will take advantage of anyone they think they can manipulate, whether they have an IQ of 60 or 140,” he said.

Reilly, 22, is a Muslim convert who has spent time detained in a mental health hospital. He has been described as a shambling introvert with the mental age of a 10-year-old. He is believed to have Asperger’s syndrome, a form of autism, and may also suffer from schizophrenia."